Golf balls

ABSTRACT

Disclosed herein are golf balls having a thermoplastic outer cover layer formed from a thermoplastic polyurethane composition. The golf balls are produced without the use of a secondary treatment step that would result in the crosslinking of the polyurethane cover composition.

FIELD OF THE INVENTION

The present invention relates generally to golf balls having a thermoplastic cover layer formed from a thermoplastic polyurethane composition having desirable shear durability without the need for a secondary curing or treatment step.

BACKGROUND OF THE INVENTION

Thermoplastic polyurethane (TPU) materials are known to be useful as golf ball cover materials. However, in order for golf ball covers formed from TPU materials to have desirable shear durability, secondary processes that crosslink the TPU material are required. For example, as disclosed in U.S. Pat. No. 6,935,970 to Matroni et al., the polyurethane cover is treated with a secondary curing or treating agent, such as a solution containing one or more isocyanates, to improve the durability of the cover. Secondary treatments with isocyanate add considerable costs to the manufacturing process. Thus, it is desirable to produce a TPU golf ball cover material that has desirable shear durability without the need for a secondary crosslinking treatment.

SUMMARY OF THE INVENTION

The present invention provides a TPU cover material that has desirable shear durability without the need for a secondary curing or treatment step. The present invention further provides particularly suitable golf ball constructions including such cover materials.

In a particular embodiment, the present invention is directed to a method of making a golf ball, the method comprising providing a golf ball subassembly comprising a core and an intermediate layer and having an adhesive coating applied to the outer surface thereof; injection molding a thermoplastic polyurethane composition about the golf ball subassembly to form a golf ball cover disposed about the golf ball subassembly; and, optionally, applying one or more coating layers to the golf ball cover to form a finished golf ball. The method does not include a step of treating the outer surface of the golf ball cover to further crosslink the thermoplastic polyurethane composition. The injection molding step includes the use of a mold cavity that includes a plurality of retractable positioning pins to hold the subassembly in the spherical center of the mold during the injection molding process, and each retractable positioning pin forms one of a plurality of dimples on the outer surface of the golf ball.

In another particular embodiment, the present invention is directed to a golf ball comprising a thermoset rubber core, a thermoplastic intermediate layer, and a thermoplastic outer cover layer. The thermoset rubber core is formed from a diene rubber composition and has a diameter of from 1.530 inches to 1.580 inches, a compression of from 55 to 70, a center Shore C hardness of from 60 to 70, an outer surface Shore C hardness of from 75 to 85, and a positive hardness gradient wherein the difference between the Shore C hardness of the outer surface of the core and the Shore C hardness of the center of the core is from 10 to 20. The thermoplastic intermediate layer is formed from an ionomer blend composition and has a thickness of from 0.020 inches to 0.040 inches and an outer surface Shore D hardness of greater than 65. The thermoplastic outer cover layer is formed from a thermoplastic polyurethane composition having a material hardness of from 48 to 55 Shore D, preferably from 49 to 53 Shore D, and has a thickness of from 0.030 inches to 0.040 inches. An adhesive layer is optionally disposed between the intermediate layer and the outer cover layer.

One or more coating layers is disposed about the outer cover layer. The ratio of the molecular weight of the thermoplastic polyurethane composition prior to molding the outer cover layer to the molecular weight of the thermoplastic polyurethane composition after molding the outer cover layer is from 3 to 50. The golf ball has a plurality of dimples on the spherical outer surface thereof, wherein the plurality of dimples are arranged in eight triangular dimple sections that are defined by projecting the eight faces of a square dipyramid onto the spherical outer surface of the ball, the eight triangular dimple sections being substantially identical in size and dimple arrangement.

DETAILED DESCRIPTION

Golf balls of the present invention have a thermoplastic outer cover layer formed from a thermoplastic polyurethane (TPU). For purposes of the present disclosure, the term “thermoplastic” in reference to a golf ball layer indicates that the entire layer, from inner surface to outer surface, is melt processable. Conventional TPU compositions used to form golf ball cover layers require a secondary treatment step, which crosslinks at least a portion of the molded cover layer, in order to provide the golf ball cover with desirable shear durability. TPU compositions of the present invention do not require such post-molding treatment step, thereby allowing for an entire layer formed therefrom to be fully melt processable.

Typical secondary treatment steps which are expressly meant to be excluded from the method of the present invention include known processes for treating a molded polyurethane golf ball cover to further crosslink the polyurethane. Particular examples of excluded secondary treatment steps include applying a curing agent, such as a solution containing one or more isocyanates, by dipping, wiping, soaking, brushing, or spraying the molded golf ball cover in/with the solution; and applying energy from a suitable source to the molded golf ball cover using, e.g., gamma radiation, ultraviolet radiation, or electron beam radiation.

Polyurethanes generally comprise the reaction product of a polyisocyanate, a polyol, and a curing agent. Particularly suitable for the present invention are polyurethanes comprising the reaction product of an aliphatic or aromatic polyisocyanate, a polyether or polyester polyol, and a curing agent. In a particular embodiment, the polyurethane is the reaction product of an aromatic polyisocyanate, a polyether polyol, and a curing agent. In a particular aspect of this embodiment, the aromatic polyisocyanate is selected from methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and naphthalene diisocyanate (NDI). In another particular aspect of this embodiment, the polyether polyol is selected from polytetramethylene ether glycol (PTMEG), polypropylene glycol, polyethylene propylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, poly(oxypropylene oxyethylene) glycol, and combinations of two or more thereof.

The curing agent may consist of a single curing agent or comprise a combination of two or more curing agents, and optionally includes a freezing point depressing agent. Suitable curing agents include, but are not limited to, hydroxy-terminated curing agents, amine-terminated curing agents, and combinations thereof. The curing agent may be saturated or unsaturated. Non-limiting examples of suitable curatives include 1,4-butanediol; 1,3-butanediol; 1,2-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; propylene glycol, dipropylene glycol; polypropylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; ethylene glycol; diethylene glycol; polyethylene glycol; resorcinol-di(beta-hydroxyethyl)ether and its derivatives; hydroquinone-di(beta-hydroxyethyl)ether and derivatives thereof 2-propanol-1,1′-phenylaminobis; trimethylolpropane; 4,4′-methylenebis(2-chloroaniline); 3,5-dimethylthio-2,4-toluenediamine; 3,5-dimethylthio-2,6-toluenediamine; 4,4′-methylenebis(2-ethylaniline); 4,4′-bis-(sec-butylamino)-diphenylmethane; 1,3-bis-(2-hydroxyethoxy)benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene; 1,4-bis-(sec-butylamino) benzene; 1,2-bis-(sec-butylamino)benzene; 3,5-diethyltoluene-2,4-diamine; 3,5-diethyltoluene-2,6-diamine; tetra-(2-hydroxypropyl)-ethylenediamine; N,N′-dialkyldiamino diphenyl methane; trimethyleneglycol-di-p-aminobenzoate; polytetramethyleneoxide-di-p-aminobenzoate; 4,4′-methylene bis-(3-chloro-2,6-diethylaniline); 1,4-cyclohexyldimethylol; 2-methylpentamethylene diamine; isomers and mixtures of diaminocyclohexane; isomers and mixtures of cyclohexane bis(methylamine); polytetramethylene ether glycol; isomers and mixtures of cyclohexyldimethylol; triisopropanolamine; diethylene triamine; triethylene tetramine; tetraethylene pentamine; propylene diamine; dipropylene triamine; 1,3-diaminopropane; dimethylamino propylamine; diethylamino propylamine; diethylene glycol bis-(aminopropyl)ether; imido-bis-(propylamine); monoethanolamine; diethanolamine; triethanolamine; monoisopropanolamine; diisopropanolamine; isophoronediamine; N,N′-diisopropyl-isophoronediamine; polyoxypropylene diamine; propylene oxide-based triamine; 3,3′-dimethyl-4,4′-diaminocyclohexylmethane; 1,5-pentanediol; 1,6-hexanediol; glycerol; 1,3-bis-(2-hydroxyethoxy)cyclohexane; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; N,N,N′,N′-tetra-(2-hydroxypropyl-ethylene) diamine; ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyl diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine; 4,4′-bis-(sec-butylamino)-dicyclohexylmethane and derivatives thereof; 1,4-bis-(sec-butylamino)-cyclohexane; 1,2-bis-(sec-butylamino)-cyclohexane; 4,4′-dicyclohexylmethane diamine; and combinations thereof.

The curing agent optionally comprises a freezing point depressing agent so that the freezing point of the blend is less than its normal freezing point temperature. The freezing point depressing agent is preferably compatible with the curing agent. For example, hydroxy-terminated curing agents, such as 1,4-butanediol, may be modified with a hydroxy-terminated freezing point depressing agent or a mixture of hydroxy-terminated freezing point depression agents. Examples of hydroxy-terminated freezing point depressing agents include, but are not limited to, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-butanediol, 1,3-butanediol, ethylene glycol, diethylene glycol, 1,5-pentanediol, polytetramethylene glycol, propylene glycol, dipropylene glycol, and combinations thereof. Similarly, amine-terminated curing agents, such as hexamethylene diamine, may be modified with an amine-terminated freezing point depressing agent or a mixture of amine-terminated freezing point depressing agents. Examples of amine-terminated freezing point depressing agents include, but are not limited to, ethylene diamine, 1,3-diaminopropane, dimethylamino propylamine, tetraethylene pentamine, 1,2-propylenediamine, diethylaminopropylamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, and combinations thereof. The freezing point depressing agent is preferably added in an amount sufficient to reduce the freezing point of the curing agent by a suitable amount to prevent loss of pigment dispersion, but not affect the physical properties of the golf ball. Freezing point depressing agents are further disclosed, for example, in U.S. Pat. No. 7,888,449 to Wu, the entire disclosure of which is hereby incorporated herein by reference.

A catalyst is optionally employed to promote the reaction. Suitable catalysts include, but are not limited to bismuth catalysts; zinc octoate; stannous octoate; tin catalysts, e.g., bis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate, tin (II) chloride, tin (IV) chloride, bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, and di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts, e.g., triethylenediamine, triethylamine, and tributylamine; organic acids, e.g., oleic acid and acetic acid; delayed catalysts, e.g., Polycat® catalysts, commercially available from Air Products and Chemicals, Inc.; and combinations thereof.

By the present invention, it has been found that molding golf ball covers using particular thermoplastic polyurethanes under particular molding conditions provides for golf ball covers having good shear durability without the need for a secondary treatment step. In particular, good shear durability results when using materials and molding conditions such that the ratio of the molecular weight of the TPU prior to molding a cover therefrom to that of the molded TPU cover is 3 or 5 or 10 or 50 or 60 or 75 or is within a range having an upper limit and a lower limit selected from these values. In a particular embodiment of the present invention, the thermoplastic polyurethane cover composition is a high molecular weight polyurethane, preferably having a weight average molecular weight (absolute), prior to molding, of at least 100,000, or at least 120,000, or at least 125,000, or at least 130,000, or at least 140,000, or at least 150,000.

Suitable polyisocyanates, polyols, curing agents, and catalysts are further disclosed, for example, in U.S. Pat. No. 8,865,052 to Makal et al., U.S. Pat. No. 6,734,273 to Onder et al., U.S. Pat. No. 8,034,873 to Siddhamalli et al.; the entire disclosures of which are hereby incorporated herein by reference. Suitable UV absorbers that are optionally included in the cover layer composition are further disclosed, for example, in U.S. Pat. No. 5,156,405 to Kitaoh; U.S. Pat. No. 5,840,788 to Lutz; and U.S. Pat. No. 7,722,483 to Morgan; the entire disclosures of which are hereby incorporated herein by reference.

Golf balls of the present invention are multilayer balls having a single- or dual-layer core, an outer cover layer, and, optionally one or more intermediate layers disposed between the core and the outer cover layer. Preferably, the outer cover layer is formed from a thermoplastic polyurethane, as further described above. The core and optional intermediate layers are formed from any suitable golf ball composition, including thermosetting materials, such as polybutadiene, styrene butadiene, isoprene, polyisoprene, and trans-isoprene; and thermoplastics, such as ionomer resins, polyamides and polyesters. Particularly preferred core compositions are thermosetting rubber compositions comprising a base polymer, an initiator agent, a coagent and/or a curing agent, and optionally one or more of a metal oxide, metal fatty acid or fatty acid, antioxidant, soft and fast agent, fillers, and additives. Suitable base polymers include natural and synthetic rubbers including, but not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), styrene-butadiene rubber, styrenic block copolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber, halobutyl rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers and plastomers, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, acrylonitrile butadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, polyalkenamers, and combinations of two or more thereof. Suitable initiator agents include organic peroxides, high energy radiation sources capable of generating free radicals, C-C initiators, and combinations thereof. Suitable coagents include, but are not limited to, metal salts of unsaturated carboxylic acids; unsaturated vinyl compounds and polyfunctional monomers (e.g., trimethylolpropane trimethacrylate); phenylene bismaleimide; and combinations thereof. Suitable curing agents include, but are not limited to, sulfur; N-oxydiethylene 2-benzothiazole sulfenamide; N,N-di-ortho-tolylguanidine; bismuth dimethyldithiocarbamate; N-cyclohexyl 2-benzothiazole sulfenamide; N,N-diphenylguanidine; 4-morpholinyl-2-benzothiazole disulfide; dipentamethylenethiuram hexasulfide; thiuram disulfides; mercaptobenzothiazoles; sulfenamides; dithiocarbamates; thiuram sulfides; guanidines; thioureas; xanthates; dithiophosphates; aldehyde-amines; dibenzothiazyl disulfide; tetraethylthiuram disulfide; tetrabutylthiuram disulfide; and combinations thereof. Suitable types and amounts of base polymer, initiator agent, coagent, filler, and additives are more fully described in, for example, U.S. Pat. Nos. 6,566,483, 6,695,718, 6,939,907, 7,041,721 and 7,138,460, the entire disclosures of which are hereby incorporated herein by reference. Particularly suitable diene rubber compositions are further disclosed, for example, in U.S. Patent Application Publication No. 2007/0093318, the entire disclosure of which is hereby incorporated herein by reference.

Particularly suitable intermediate layer materials include, but are not limited to:

-   -   a) polyurethanes, polyureas, and hybrids of polyurethane and         polyurea;     -   b) E/X- and E/X/Y-type ionomers, wherein E is an olefin (e.g.,         ethylene), X is a carboxylic acid (e.g., acrylic, methacrylic,         crotonic, maleic, fumaric, or itaconic acid), and Y is a         softening comonomer (e.g., vinyl esters of aliphatic carboxylic         acids wherein the acid has from 2 to 10 carbons, alkyl ethers         wherein the alkyl group has from 1 to 10 carbons, and alkyl         alkylacrylates such as alkyl methacrylates wherein the alkyl         group has from 1 to 10 carbons), such as Surlyn® ionomer resins         and DuPont® HPF 1000 and HPF 2000, commercially available         from E. I. du Pont de Nemours and Company, Iotek® ionomers,         commercially available from ExxonMobil Chemical Company,         Amplify® IO ionomers of ethylene acrylic acid copolymers,         commercially available from The Dow Chemical Company, and         Clarix® ionomer resins, commercially available from A. Schulman         Inc.;     -   c) polyisoprene;     -   d) polyoctenamer, such as Vestenamer® polyoctenamer,         commercially available from Evonik Industries;     -   e) polyethylene, including, for example, low density         polyethylene, linear low density polyethylene, and high density         polyethylene; polypropylene;     -   f) rubber-toughened olefin polymers; non-ionomeric acid         copolymers, e.g., (meth)acrylic acid, which do not become part         of an ionomeric copolymer;     -   g) plastomers;     -   h) flexomers;     -   i) styrene/butadiene/styrene block copolymers;     -   j) styrene/ethylene-butylene/styrene block copolymers;     -   k) polybutadiene;     -   l) styrene butadiene rubber;     -   m) ethylene propylene rubber;     -   n) ethylene propylene diene rubber;     -   o) dynamically vulcanized elastomers;     -   p) ethylene vinyl acetates;     -   q) ethylene (meth) acrylates;     -   r) polyvinyl chloride resins;     -   s) polyamides, amide-ester elastomers, and copolymers of ionomer         and polyamide, including, for example, Pebax® thermoplastic         polyether and polyester amides, commercially available from         Arkema Inc;     -   t) crosslinked trans-polyisoprene;     -   u) polyester-based thermoplastic elastomers, such as Hytrel®         polyester elastomers, commercially available from E. I. du Pont         de Nemours and Company, and Riteflex® polyester elastomers,         commercially available from Ticona;     -   v) polyurethane-based thermoplastic elastomers, such as         Elastollan® polyurethanes, commercially available from BASF;     -   w) synthetic or natural vulcanized rubber;     -   x) and combinations thereof.

Compositions comprising an ionomer or a blend of two or more E/X- and E/X/Y-type ionomers are particularly suitable intermediate layer materials. Preferred E/X- and E/X/Y-type ionomeric compositions include:

-   -   (a) a composition comprising a “high acid ionomer” (i.e., having         an acid content of greater than 16 wt %), such as Surlyn® 8150;     -   (b) a composition comprising a high acid ionomer and a maleic         anhydride-grafted non-ionomeric polymer (e.g., Fusabond®         functionalized polymers). A particularly preferred blend of high         acid ionomer and maleic anhydride-grafted polymer is a 84 wt %         16 wt % blend of Surlyn® 8150 and Fusabond®. Blends of high acid         ionomers with maleic anhydride-grafted polymers are further         disclosed, for example, in U.S. Pat. Nos. 6,992,135 and         6,677,401, the entire disclosures of which are hereby         incorporated herein by reference;     -   (c) a composition comprising a 50/45/5 blend of Surlyn®         8940/Surlyn® 9650/Nucrel® 960, preferably having a material         hardness of from 80 to 85 Shore C;     -   (d) a composition comprising a 50/25/25 blend of Surlyn®         8940/Surlyn® 9650/Surlyn® 9910, preferably having a material         hardness of about 90 Shore C;     -   (e) a composition comprising a 50/50 blend of Surlyn®         8940/Surlyn® 9650, preferably having a material hardness of         about 86 Shore C;     -   (f) a composition comprising a blend of Surlyn® 7940/Surlyn®         8940, optionally including a melt flow modifier;     -   (g) a composition comprising a blend of a first high acid         ionomer and a second high acid ionomer, wherein the first high         acid ionomer is neutralized with a different cation than the         second high acid ionomer (e.g., 50/50 blend of Surlyn® 8150 and         Surlyn® 9150), optionally including one or more melt flow         modifiers such as an ionomer, ethylene-acid copolymer or ester         terpolymer; and     -   (h) a composition comprising a blend of a first high acid         ionomer and a second high acid ionomer, wherein the first high         acid ionomer is neutralized with a different cation than the         second high acid ionomer, and from 0 to 10 wt % of an         ethylene/acid/ester ionomer wherein the ethylene/acid/ester         ionomer is neutralized with the same cation as either the first         high acid ionomer or the second high acid ionomer or a different         cation than the first and second high acid ionomers (e.g., a         blend of 40-50 wt % Surlyn® 8140 or 8150, 40-50 wt % Surlyn®         9120, and 0-10 wt % Surlyn® 6320).

Surlyn® 8150®, Surlyn® 8940, and Surlyn® 8140 are different grades of E/MAA copolymer in which the acid groups have been partially neutralized with sodium ions. Surlyn® 9650, Surlyn® 9910, Surlyn® 9150, and Surlyn® 9120 are different grades of E/MAA copolymer in which the acid groups have been partially neutralized with zinc ions. Surlyn® 7940 is an E/MAA copolymer in which the acid groups have been partially neutralized with lithium ions. Surlyn® 6320 is a very low modulus magnesium ionomer with a medium acid content. Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt % methacrylic acid. Surlyn® ionomers, Fusabond® polymers, and Nucrel® copolymers are commercially available from E. I. du Pont de Nemours and Company.

Suitable E/X- and E/X/Y-type ionomeric cover materials are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated by reference.

Suitable conventional polyurethanes, polyureas, and blends and hybrids of polyurethane/polyurea for use in forming layers other than the outer cover layer are further disclosed, for example, in U.S. Pat. Nos. 5,334,673, 5,484,870, 6,506,851, 6,756,436, 6,835,794, 6,867,279, 6,960,630, and 7,105,623; U.S. Patent Application Publication Nos. 2009/0011868 and 2007/0117923; and U.S. Patent Application No. 60/401,047, the entire disclosures of which are hereby incorporated herein by reference.

Dimensions of golf ball components, i.e., thickness and diameter, may vary depending on the desired properties.

Golf ball cores of the present invention include single, dual, and multilayer cores, and preferably have an overall diameter within the range having a lower limit of 0.75 inches or 1 inch or 1.25 inches or 1.4 inches and an upper limit of 1.55 inches or 1.6 inches or 1.62 inches or 1.63 inches.

In a particular embodiment, the core is a solid, single layer having a diameter within a range having a lower limit of 0.750 or 1.00 or 1.10 or 1.15 or 1.20 or 1.25 or 1.30 or 1.40 or 1.50 or 1.53 or 1.55 inches and an upper limit of 1.55 or 1.60 or 1.62 or 1.63 or 1.65 inches. In a particular aspect of this embodiment, the core has a center Shore C hardness of 95 or less, or 90 or less, or 85 or less, or 80 or less, or a center Shore C hardness within a range having a lower limit of 20 or 25 or 30 or 35 or 40 or 45 or 50 or 55 or 60 or 65 or 70 or 75 and an upper limit of 60 or 65 or 70 or 75 or 80 or 83 or 85 or 90 or 95, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 65, the upper limit is 70, 75, 80, 83, 85, 90, or 95). In another particular aspect of this embodiment, the core has an outer surface Shore C hardness of 50 or greater, or 55 or greater, or 60 or greater, or 65 or greater, or 70 or greater, or an outer surface Shore C hardness within a range having a lower limit of 40 or 45 or 50 or 55 or 60 or 65 or 70 or 74 and an upper limit of 60 or 65 or 70 or 74 or 75 or 78 or 80 or 85 or 90 or 95, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 65, the upper limit is 70, 74, 75, 78, 80, 85, 90, or 95). In another particular aspect of this embodiment, the core has a low negative, low positive, or zero hardness gradient. In another particular aspect of this embodiment, the core is formed from a substantially homogeneous formulation and has a hardness gradient wherein the difference between the Shore C hardness of the outer surface and the Shore C hardness of the center of the core is within a range having a lower limit of -8 or -5 or -3 or 0 and an upper limit of 0 or 3 or 5 or 8 or 10 or 15 or 18 or 20 or 25 or 30. In another particular aspect of this embodiment, the core has a compression of 90 or less, or 80 or less, or 75 or less, or 70 or less, or a compression within a range having a lower limit of 50 or 55 or 60 or 65 and an upper limit of 65 or 70 or 75 or 80 or 90.

In another particular embodiment, the core comprises an inner core layer and an outer core layer, the inner core layer having a diameter within a range having a lower limit of 0.900 or 0.910 or 0.920 or 0.930 or 0.940 or 0.950 or 0.960 or 0.970 or 0.980 or 0.990 or 1.000 or 1.010 or 1.020 inches and an upper limit of 1.020 or 1.030 or 1.040 or 1.050 or 1.060 or 1.070 or 1.080 or 1.090 or 1.100 or 0.110 or 1.120 or 1.130 inches, and the outer core having a thickness within the range having a lower limit of 0.050 or 0.100 or 0.200 or 0.250 inches and an upper limit of 0.280 or 0.310 or 0.440 or 0.500 inches. In a particular aspect of this embodiment, the inner core layer has a center Shore C hardness of 95 or less, or 90 or less, or 85 or less, or 80 or less, or 75 or less, or a center Shore C hardness within a range having a lower limit of 20 or 25 or 30 or 35 or 40 or 45 or 50 or 55 or 60 or 65 or 70 or 75 and an upper limit of 60 or 65 or 70 or 75 or 80 or 83 or 85 or 90 or 95, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 65, the upper limit is 70, 75, 80, 83, 85, 90, or 95). In another particular aspect of this embodiment, the inner core layer has an outer surface Shore C hardness of 50 or greater, or 55 or greater, or 60 or greater, or 65 or greater, or an outer surface Shore C hardness within a range having a lower limit of 40 or 45 or 50 or 55 or 60 or 65 or 70 or 74 and an upper limit of 60 or 65 or 70 or 74 or 75 or 78 or 80 or 85 or 90 or 95, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 65, the upper limit is 70, 74, 75, 78, 80, 85, 90, or 95). In another particular aspect of this embodiment, the inner core layer has a negative or zero hardness gradient. In another particular aspect of this embodiment, the inner core layer is formed from a substantially homogeneous formulation and the difference between the Shore C hardness of the outer surface of the inner core layer and the Shore C hardness of the center of the inner core layer is within a range having a lower limit of −20 or −15 or −10 and an upper limit of −10 or −5 or 0. In another particular aspect of this embodiment, the inner core layer has a compression of 50 or less, or 40 or less, or 30 or less, or a compression within a range having a lower limit of 10 or 15 or 20 or 25 and an upper limit of 25 or 30 or 40 or 50 or 65. In another particular aspect of this embodiment, the outer core layer has an outer surface Shore C hardness within a range having a lower limit of 70 or greater, or 75 or greater, or 80 or greater, or 85 or greater, or 89 or greater, or an outer surface Shore C hardness within a range having a lower limit of 70 or 75 or 80 or 85 or 89 and an upper limit of 80 or 85 or 90 or 93 or 95, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 85, the upper limit is 90, 93, or 95). In another particular aspect of this embodiment, the core has an overall dual core compression within a range having a lower limit of 60 or 70 or 80 or 85 and an upper limit of 85 or 90 or 95.

Golf balls of the present invention preferably have a compression of 70 or 75 or 80 or 85 or 100 or 105 or a compression within a range having an upper limit and a lower limit selected from these values. Golf ball of the present invention preferably have a coefficient of restitution (COR) of 0.770 or 0.780 or 0.800 or 0.820 or a COR within a range having an upper limit and a lower limit selected from these values.

In a particularly preferred embodiment, golf balls of the present invention have a thermoset rubber core, a thermoplastic intermediate layer, and a thermoplastic outer cover layer formed from a thermoplastic polyurethane composition.

The core is preferably formed from a diene rubber composition, and preferably has a diameter of 1.500 or 1.510 or 1.530 or 1.550 or 1.560 or 1.580 inches or a diameter within a range having an upper limit and a lower limit selected from these values. The core preferably has a compression of 50 or 55 or 60 or 65 or 70 or 75 or a compression within a range having an upper limit and a lower limit selected from these values. The core preferably has a center Shore C hardness of 50 or 60 or 65 or 70 or 80 or a center Shore C hardness within a range having an upper limit and a lower limit selected from these values. The core preferably has an outer surface Shore C hardness of 65 or 70 or 75 or 80 or 85 or 90 or 95 or an outer surface Shore C hardness within a range having an upper limit and a lower limit selected from these values. The core preferably has an overall positive hardness gradient wherein the Shore C hardness of the outer surface of the core is greater than the Shore C hardness of the center of the core and the difference there between is 5 or 10 or 15 or 18 or 20 or 25 or 30 or the difference there between is within a range having an upper limit and a lower limit selected from these values.

The intermediate layer is preferably formed from an ionomer blend composition and has a thickness of 0.010 or 0.020 or 0.030 or 0.040 or 0.050 inches or a thickness within a range having an upper limit and a lower limit selected from these values. The intermediate layer preferably has an outer surface Shore D hardness of greater than 55 or greater than 60 or greater than 65. Preferably, a golf ball subassembly consisting of the core and the intermediate layer has an outer diameter of 1.580 or 1.590 or 1.600 or 1.610 or 1.620 inches or an outer diameter within a range having an upper limit and a lower limit selected from these values.

The outer cover layer is formed from a thermoplastic polyurethane composition and preferably has a thickness of 0.020 or 0.030 or 0.035 or 0.040 or a thickness within a range having an upper limit and a lower limit selected from these values. The outer cover layer composition preferably has a material hardness of 45 or 48 or 50 or 55 or 60 Shore D or a material hardness within a range having an upper limit and a lower limit selected from these values. The outer cover layer preferably has an outer surface hardness of 80 or 82 or 85 or 88 Shore C or an outer surface hardness within a range having an upper limit and a lower limit selected from these values.

Golf balls are typically finished by applying one or more finishing coats over the cover. For example, a primer and a topcoat may be applied. Either or both of the primer and topcoat compositions may be pigmented or clear. Several coats of clear or pigmented coatings may be applied.

Primer and topcoat compositions are typically a solvent-borne or water-borne material, particularly selected from, but not limited to, polyurethanes, polyureas, acrylic polyurethanes, polyesters, polyester acrylics, and epoxies. In a particular embodiment, golf balls of the present invention comprise at least one coat of primer and at least one coat of topcoat. In a particular aspect of this embodiment, the primer is a clear waterborne composition and the topcoat is a clear solventborne composition. In a further particular aspect of this embodiment, the topcoat composition includes an optical brightener in a concentration of about 0.01 to about 0.20 weight %, and, optionally, does not include a light stabilizer. In another further particular aspect of this embodiment, the topcoat composition is a two-part solvent-borne polyurethane comprising a resin component and an isocyanate component, wherein the isocyanate component is present in an amount of from 68 parts to 71 parts, by weight per 100 parts of the resin component, the resin component comprises from 46 to 52 wt % solids, and the isocyanate component comprises from 46 to 53 wt % solids.

Non-limiting examples of suitable coatings are further disclosed, for example, in U.S. Pat. Nos. 5,409,233; 5,459,220; 5,494,291; 5,820,491; 5,669,831; 5,817,735; and 7,935,421, the entire disclosure of which are hereby incorporated herein by reference

The present invention is also directed to a method of making a golf ball. The method comprises the steps of providing a golf ball subassembly comprising a core and an intermediate layer and, optionally, an adhesive coating applied to the outer surface of the subassembly; injection molding a thermoplastic polyurethane composition about the golf ball subassembly to form a dimpled, unfinished golf ball; and applying one or more coating layers to the dimpled, unfinished golf ball to form a finished golf ball. The method does not include a step of treating the outer surface of the unfinished golf ball to further crosslink the thermoplastic polyurethane composition.

The injection molding step includes the use of a mold cavity that includes a plurality of retractable positioning pins to hold the subassembly in the spherical center of the mold during the injection molding process, and each retractable positioning pin forms one of a plurality of dimples on the outer surface of the golf ball. In a preferred embodiment, four retractable positioning pins are used on each mold half. Thus, in this embodiment, the retractable pins form four of the dimples on each hemisphere of the golf ball.

In a particular embodiment, the overall dimple pattern on the golf ball is defined by a square dipyramid wherein the dimples are arranged in eight triangular dimple sections that are defined by projecting the eight faces of a square dipyramid onto the spherical outer surface of the ball, the eight triangular dimple sections being substantially identical in size and dimple arrangement. In a particular aspect of this embodiment, the dimple arrangement within each of the eight triangular sections is not rotationally symmetric about the center of the section. In another particular aspect of this embodiment, from 2% to 10% of the dimples have an elliptical plan shape. In another particular aspect of this embodiment, the dimples having an elliptical plan shape correspond to the dimples formed by the retractable positioning pins during the injection molding process. Suitable dimple patterns based on a square dipyramid are further disclosed, for example in U.S. patent application Ser. No. 16/587,298, filed Sep. 30, 2019, U.S. patent application Ser. No. 16/587,321, filed Sep. 30, 2019, and U.S. patent application Ser. No. 16/587,455, filed Sep. 30, 2019, the entire disclosures of which are hereby incorporated herein by reference.

Golf balls of the present invention preferably have an overall dimple surface coverage of 75% or greater, or 78% or greater, or 80% or greater, and, preferably, the total number of dimples is 320 or 322 or 328 or 330 or 336 or 338 or 344 or 346 or 352 or 354 or 360 or 362 or 368 or 370 or the total number of dimples is within a range having a lower limit and an upper limit selected from these values.

At the end of a single cycle of the injection molding process, the outer cover layer material that is left within the runners leading to the ball cavity mold is optionally ground and added back into the TPU composition for use during another injection molding cycle. This material is referred to in the examples below as regrind.

EXAMPLES

The following non-limiting examples demonstrate TPU outer cover layer materials and golf ball cover layers formed therefrom, made in accordance with the present invention. The examples are merely illustrative of the preferred embodiments of the present invention, and are not to be construed as limiting the invention, the scope of which is defined by the appended claims.

Table 1 below shows the absolute molecular weight values, relative molecular weight values, and polydispersity (PD), prior to and after molding, of Texin® 1049 aromatic polyether-based polyurethane, commercially available from Covestro.

TABLE 1 Texin ® 1049 absolute absolute absolute M_(n) M_(w) M_(z) PD virgin pellets 33,620 85,106 241,247 2.531 regrind 29,448 61,440 137,066 2.086 molded cover - virgin pellets 14,799 29,787 48,795 2.013 molded cover - 50% virgin 14,598 29,285 46,797 2.006 pellets, 50% regrind molded cover - 100% regrind 11,126 28,180 46,574 2.533 masterbatch 14,974 28,725 45,083 1.918 relative relative relative M_(n) M_(w) M_(z) PD virgin pellets 44,360 145,612 317,451 3.282 regrind 34,598 103,060 211,538 2.979 molded cover - virgin pellets 19,763 53,185 102,081 2.691 molded cover - 50% virgin 19,131 50,996 95,796 2.665 pellets, 50% regrind molded cover - 100% regrind 19,450 49,830 92,285 2.562 masterbatch 16,214 46,437 79,228 2.864

Table 2 below shows the absolute molecular weight values, relative molecular weight values, and polydispersity (PD), prior to and after molding, of Estane ® ETE 50DT3 aromatic polyether-based polyurethane, commercially available from Lubrizol.

TABLE 2 Estane ® ETE 50DT3 absolute absolute absolute M_(n) M_(w) M_(z) PD virgin pellets 80,309 151,150 288,514 1.882 regrind 47,414 97,781 192,942 2.062 molded cover - virgin pellets 22,394 50,078 83,750 2.236 molded cover - 50% virgin 26,482 49,110 83,343 1.854 pellets, 50% regrind molded cover - 100% regrind 20,807 42,917 71,550 2.063 white masterbatch 22,678 32,913 47,406 1.451 relative relative relative M_(n) M_(w) M_(z) PD virgin pellets 61,428 236,384 487,066 3.848 regrind 44,254 145,252 298,415 3.282 molded cover - virgin pellets 28,871 84,843 167,237 2.939 molded cover - 50% virgin 27,239 82,042 164,248 3.012 pellets, 50% regrind molded cover - 100% regrind 23,996 71,557 143,630 2.982 white masterbatch 21,422 49,722 85,560 2.321

In the above examples, covered golf balls were formed by injection molding the TPU outer cover layer materials about a cased core such that the cover has a thickness of about 0.350 inches. The cased core consists of a 1.550 inch diameter polybutadiene core having a center hardness of about 64 Shore C, an outer surface hardness of about 79 Shore C, and a compression of about 65, and an intermediate layer formed from a 50/50 blend of Surlyn® 8150/Surlyn® 9120 and having a thickness of about 0.030 inches and an outer surface hardness of about 68 Shore D.

When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used.

All patents, publications, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains. 

1. A golf ball consisting essentially of: a thermoset rubber core formed from a diene rubber composition and having a diameter of from 1.530 inches to 1.580 inches, a center Shore C hardness of from 60 to 70, an outer surface Shore C hardness of from 75 to 85, and a positive hardness gradient wherein the difference between the Shore C hardness of the outer surface of the core and the Shore C hardness of the center of the core is from 10 to 20; a thermoplastic intermediate layer formed from an ionomer blend composition and having a thickness of from 0.020 inches to 0.040 inches and an outer surface Shore D hardness of greater than 65; a thermoplastic outer cover layer formed from a thermoplastic polyurethane having a material hardness of from 48 to 55 Shore D and having a thickness of from 0.030 inches to 0.040 inches; an optional adhesive coating disposed between the intermediate layer and the outer cover layer; and one or more coatings disposed about the outer cover layer; wherein the ratio of the molecular weight of the thermoplastic polyurethane composition prior to molding the outer cover layer to the molecular weight of the thermoplastic polyurethane composition after molding the outer cover layer is from 3 to 50; and wherein the golf ball has a plurality of dimples on the spherical outer surface thereof, wherein the plurality of dimples are arranged in eight triangular dimple sections that are defined by projecting the eight faces of a square dipyramid onto the spherical outer surface of the ball, the eight triangular dimple sections being substantially identical in size and dimple arrangement.
 2. The golf ball of claim 1, wherein the golf ball includes a waterborne primer coating and a solventborne top coating.
 3. The golf ball of claim 1, wherein the dimple arrangement within each of the eight triangular sections is not rotationally symmetric about the center of the section; and wherein from 2% to 10% of the dimples have an elliptical plan shape. 4-6. (canceled) 